1. Field of the Invention
This invention relates to the regeneration of photographic processing solutions for re-use, particularly, to the regeneration of an intensifying solution containing a cobalt (III) complex salt.
2. Description of the Prior Art
The present invention can be applied to the regeneration of an intensifying solution, containing a cobalt (III) complex, which has been brought into contact with image-wise distributed catalytic silver formed by developing an exposed silver halide material in the presence of a developing agent and a coupler so as to obtain a desired level of image density.
According to such a method, one can obtain an image of sufficient density even with a markedly reduced amount of silver halide coated per unit area of photographic material. The solution containing a cobalt complex will be referred to as an intensifying solution. The cobalt complex salt plays the role of an oxidizing agent for the developing agent in contrast to the case of conventional silver halide color photography where silver halide oxidizes the developing agent. Thus, in the above described intensifying processing, the amount of silver halide can be remarkably reduced to such a degree as to just provide a catalytic amount of silver to promote the oxidizing reaction.
A typical embodiment of a photographic processing including such an image intensification is one for photographic color materials with a reduced coated amount of silver halide, whereby the material is processed after image-wise exposure with a color developer to provide image-wise distributed developed silver and also to the imbibe color developing agent sufficiently into the photographic layer, and then is treated with an intensifying solution containing a cobalt complex salt to allow oxidative coupling of the color developing agent, thus providing an image of sufficient density. Development and intensification need not necessarily be carried out by successive treatments; instead, both may be combined in a mono-bath processing.
More specific details of image intensification are described in Japanese patent application No. 76101/74 and in Japanese patent applications (OPI) Nos. 9728/73 and 9729/73.
While photographic processing including image intensification as described permits a reduction of the coating amount of silver halide in photographic materials, a cobalt (III) complex salt must be used as the main component of the intensifying solution. Therefore, it is significant, from the economic point of view, to utilize the cobalt complex as efficiently as possible to minimize the consumption rate thereof.
On the other hand, intensification is typically carried out immediately after development without any intervening washing; thus the intensifying solution is readily contaminated with various ingredients of the developer solution, resulting in a shift of the performance characteristics thereof.
Furthermore, waste containing a cobalt salt should not be discharged out of the system, considering environmental pollution.